A table giving each refrigerant's saturation temperature at each pressure.
A PT chart lists saturation pressure against temperature for a specific refrigerant. It lets you turn a gauge reading into a boiling or condensing temperature, which you need for superheat and subcooling.
Use the chart for the exact refrigerant in the system. For blends with glide, charts show a dew point column and a bubble point column; use dew for superheat and bubble for subcooling. A PT chart also helps spot non-condensables: a standing system at a known temperature should read close to the saturation pressure for that temperature.
Exam work areas
B · Tools, piping and refrigerant handling E · Commissioning and start-up